1. Field of the Invention
This patent application pertains to automobile navigation systems. More particularly, this patent application pertains to automobile navigation systems that use dead reckoning techniques for determining the automobile's location.
2. Description of the Related Art
Dead reckoning techniques using a method of sample measurements of compass direction and distance traveled quickly produce errors too excessive to navigate a vehicle on streets and highways. There are several patents in the art using normalization methods that correlate the dead reckoned coordinates to the roadway projected coordinates of the road map database. These patents, however, do not provide an optimal solution. In fact, they usually do not produce workable solutions except in the most simple cases, and they fail to overcome the inherent errors produced when correlating the dead reckoning path to the road map database with the result that numerous manual corrections must be made to resynchronize the current location of the automobile with the road map database.